<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <script>
        var a = 5;
        /*
        console.log(a>4 && a<4);        //&且，只要有一边是错的就是错的，两边都对才能是ture
        console.log(a>6 && a<5);
        console.log(a<6 && a>3);
        */

        console.log(a>4 || a<4);       //     ||或，只要有一边是对的就是对的,两边都是假的才是假的
        console.log(a>6 || a<5);
    </script>
</body>
</html>